[A study of mandible chewing movement in patients with developmental lateral jaw deformity].

Objective: The purpose of the present study was to investigate effects of developmental lateral jaw deformity (DLJD) on masticatory movement.

Methods: Three coordinates of mandibular movement signals were recorded in 35 young healthy adults with normal occlusion and 28 patients with DLJD by means of a Sirognathography System during gum chewing movement. Paired and unpaired t-tests were used to compare significant difference of intra-group and inter-groups in displacement and speed. P < 0.05 was chosen as significance level.

Results: (1) The rhythm and directional sequence of chewing trajectory in both frontal and sagittal planes were normal in control group, while anomalies of rhythm and distribution (n = 9) and reversed sequencing (n = 7) were found in DLJD group. (2) The maximum magnitude of jaw retrusion and average speed were significant higher in DLJD group than those in control group (P < 0.01). The spatial displacement and average speed in horizontal plane and in chewing phase were also higher in DLJD group compared with control group (P < 0.05).

Conclusions: DLJD patients showed anomalies in chewing pattern as well as chewing speed and displacement in horizontal plane.